Compressor controls



Dec. 20, 1960 N. J. JANISSE COMPRESSOR CONTROLS 2 Sheets-Sheet 1 FiledNov. 12, 1958 CONDENSER.

Final 15 P: EVAPORATOR.

THERMOS'I'A'I COMPRESSOR,

ELE CTBIC MOTOR,

LOAD

q AIR SUPPLY & a

8 ELEC TOR. VALVE.

LIMITING RELAY m e 3 s 4 b K m m n a T a Z? N M J 1 E O J m M n w w m zE 5 r 2 o q fig J owmmwmfit N K 1 DAWN 3 i: o 2 am 6% e m WM 5 s .1 P w.F m m m m L c/ A m f m 4? 1 m a s. R 4 1 L 8 7 RQ L M l 1; w, I 2 nmm mA L OMB LLB Dec. 20, 1960 N. J. JANISSE COMPRESSOR CONTROLS 2Sheets-Sheet 2 Filed Nov. 12, 1958 8 3 3 H A k 5 a a w 2 w a m Fie. 5

INVENTOR Norman J.Jan1'.sse BY @w mw ATTORNEYS United States PatentCOMPRESSOR CONTROLS Norman J. Janisse, Grafton, Wis., assignor toJohnson Service Company, Milwaukee, Wis., a corporation of WisconsinFiled Nov. 12, 1958, Ser. No. 773,248

3 Claims. (Cl. 62-209) This invention relates to means for controllingthe operation of a compressor in a refrigeration circuit of thecompressor-condenser-evaporator-type. Particularly, it relates to anautomatic control means arranged to vary the adjustment of means forvarying the rate of flow through the compressor, e.g., a throttlingmeans in the suction connection of the compressor.

The purpose of the control system according to the present invention isto provide a control in which the throttling means is normallycontrolled by a relay responsive to evaporator temperature but in whichthe control is transferred from the normally controlling relay tocontrol by a second relay when the current drawn by the compressor motoris excessive, but only when this transfer would cause a reduction inflow rate. It is well known to those skilled in the art that, undervarious conditions encountered in the normal operation of arefrigeration system, the density of the gases entering the compressorrises, thereby materially increasing the load on the compressor. Thisincreased load is particularly apparent when the refrigeration system isput into operation after it has stood idle for any extended period oftime. Under conditions of overload, the compressor motor will draw anexcessive current. Unless a motor large enough to operate under anynormally encountered overload load is used, it is necessary to providemeans to limit the current drawn by the motor. This current limitationmay be performed and usually is performed by some type of automaticmeans effective to vary the load on the compressor. This load-varyingmeans may take a variety of forms. It may be, as has been suggestedabove, a throttling valve to vary the rate of flow through thecompressor. If a reciprocating piston-type of compressor is being used,the control system may be actuated so as to remove the load from one ormore of the pistons or to increase the clearance space in the compressorcylinders, or it may be a control which will hold either the suction orthe exhaust valves of the compressor open. All of these forms of controlare well known in the art, and the present invention is usefulregardless of the type of flow-rate-varying control which is used in thecompressor. According to the present invention the throttling means, inthe compressor suction connection, is provided with a fluidpressure-operated actuator which is operable to shift the throttlingmeans through its adjusting range. This fluid pressure actuator isselectively controlled by either of two fluid pressure-actuated relays.These relays may be of either the Class I type or of the Class II type;the terms Class I and Class II being in every day use in the industryand'designating, respectively, a direct-acting and a reverse-actingrelay. Each relay is of a different class. A selector valve mechanism isprovided which-has two inlets, one connected to the branch line of oneof the relays and the other to the branch line of the other relay.

The selector valve mechanism has a single outlet which is connected withthe fluid pressure-operatedactuator. The selector valve mechanismincludes a motor connected to shift the selector valve between. twooperating posi- 2,984,925 Patented Dec. 20, 1960 tions, namely, aposition in which it connects one of its inlets in flow communicationwith its outlet, and a second position in which it connects the other ofits inlets with its outlet. The valve shifting motor includes twoopposed working spaces; each working space being connected in flowcommunication with a ditferent branch line. The valve shifting motoracts in response to the difference between the pressures in therespective branch lines to interconnect its outlet with that branch linewhose pressure will cause the actuator to shift the throttling means toproduce the lower rate of flow through the compressor.

The first relay is responsive to a temperature produced by theevaporator. The second relay is responsive to the amount by which thecurrent drawn by the electric motor driving the compressor exceeds apredetermined value.

It is preferred that the thermostat be a Class I instrument. Since thecurrent-responsive relay is of the other class, it will be a Class IIinstrument. The valve actuator will cause the throttle to close as thepressure it receives falls. In this preferred form, the selector valvewill select the lowerbranch line pressure for transmission to theactuator. This embodiment is preferred for the reason that if eitherbranch line is damaged or ruptured, the selector valve will connect thatbranch line to the actuator, causing the throttling means to assume theposition in which the minimum rate of flow through the compressor isestablished. If the thermostatically con.-. trolled relay is areverse-acting instrument and the currentresponsive relay is adirect-acting instrument, the selector valve will select the higherbranch line pressure for transmission to the actuator, and the actuatorwould be of the type in which rising pressure will close the throttlevalve. The presence of the selector valve mechanism means. that theactuator is never connected simultaneously to the branch lines of bothrelays. In this way, the control function of each relay is independentof the control function of the other relay. This independent control, bydifferent relays, results in a control system whose operation isunusually stable when contrasted to control sys-- tems in which the tworelays were not selectively connected to the actuator but were connectedto it simul-'-- ice taneously.

The invention will be described having reference to-the accompanyingdrawings, in which: a 1 v 4 Fig. 1 is a diagrammatic showing of arefrigerative device equipped with a control system embodying thepresent invention. 1

' Fig. 2 is a similar diagrammatic showing of an alternate arrangementof the control system.

Fig. 3 is an axial section through the selector valve mechanism. As hereshown, the selector valve will transmit the higher of the two pressuressupplied thereto.

Fig. 4 is an axial section of the selector valve, but here shownarranged to select the lower of the supplied pres sures.

.Fig. 5 is a sectional view, partly in elevation, showing.

" a piloted relay valve used in the system illustrated in butterflyvalve 15, located in the suctionconnection of the compressor 11.- Thevalve is positioned by' a fluid pressure actuator 16. This actuator 16receives fluid pressure from a selector valvemechanisrn 17, whichselectively connects the actuator 16 with an overload 1 relay 18. orwith a thermostatically piloted relay valve The thermostat is shown at21 and, as shown, is responsive to the temperature of evaporator '13.

The relays 18 and 19 and the thermostat 21 each ress ve ai nder essu f ma air u pl identified b dnni'the d awin may it breach 1in2Is0 taqt w i lt o the e is l e 1 .siit i r the b nch l n 2 1st e y 4. is s nested t9the other inlet of the selector valve 17. The thermostats bra l 24 i onncte wi h rela '1 1.9 Pi, t ts operation; The overload relay 18 landthermostat 21 are familiar commercially available tluid pressure relayvalves Whose on ant Wel sa Wi in the entral art. While the selectorvalve 17 and the piloted relay 19 are also commerci 11 m is not so wellof these relays is e$lll ajl i nt on 1W di fers 17 a sh w :E ss

is shown in Fig.5. l

' Referring to Fig. 3, the selector valve 17 includes a housing 25' anda cover plate 26, secured together by bolts (n S Q U- Qq fines be weenthe dy an sol/er plate 26 is a reversible valve assembly 27. As shown,this valve assembly c rnprises three spaced, annular dia phragms clampedat their peripheries between the body 25, two annular spacers and coverplate 26. The periphcries of the central ppenings in'the diaphragnls arela ed be e n?! fl n e ii t e .mbna emem a 28 l 3a' l at mler s acer an?!2 nmhe b n des inlet p a es an 1whi ommun at ec iv y, th carna e shamanss2, a d as. Th od ha an e le e 'ss an 34 Web Qi mu satcs de a with 02 s?slumber 35 which 1 in urn; in on t open s mitl ni tibn with ou t Em e Chm s 35 nd m .i n ate th we a ot r by a of radial P in he tubul r al e me nd t e no s djacen rrcsi aid- Qone valves 3.6 an 1. w ich are r a enwar closed pos ive con o ow from inlet passages 29 and 3 1,respectively, to the cornmunicating outlet chambers 35 and 3.5. It willreadily be apparent that a dominant pressure in inlet 31 will shift thevalve member 28 in a direction to open cone valve 36 and interconnectinlet 31 with the outlet 34. A dominant pressure in inlet connection 29will unseat valve 37 whereby pressure is admitted to outlet 34 from theinlet 29. v

The selector valve shown in Fig. 4 is the same as that.

shown in Fig. 3 except that 'th'e valve assembly 27 has been reversed.With this assembly of the parts, a dominant pressure in the inlet 31will cause cone valve 37 to be unseated thereby admitting pressure tothe outlet 34 from the inlet connection 29S A dominant pressure in inletconnection 29 similarly will connect inlet 31 with the outlet 34. Thusit will be seen that the Fig. 3 arrangement selects the higher inletpressure for transmission to the outletQwhile the Fig, 4 arrangementcauses the lower inlet pressure to be transmitted tothe outlet. Ashasbeen pointed out, these selector valve mechanisms are commerciallyavailable More complete details concerning their construction maybehadfrom applicants assigne'e and by reference to that assigneesApparatus Bulletin C 120.

The piloted relay 19 shown in Fig. 5 is also a corn: mercially available'device and is fully'described in applicants assignees InstructionBuletin D 265 A. As shown in Fig. 5, the relay includes a housing havinga supply cpnnection 38, an outlet or branch liueconnection 39, and apilot pressure connection 41. The housing has three diaphragm chambers42, 43 and 44 therein. Eharnbers 42 and 43 are in constant opencommunication with each other and with the outlet connection 39. Asupply and43. Fluid is admitted through the supply valve front theconnection 38, and is vented through exhaust I .iaeaaaas P The supply ndexhau valve 45 is shq n i9 lap position witli b'oth the ,supply andexhaust valves closed. Upward movement of the diaphragm leaves thesupply valve closed and opens the exhaust valve. Downward movement ofthe diaphragm reverses this valving. The diaphragms in chambers 42 and43 are of equal area. -A lever 48 is pivoted to diaphragm retainer 49 atThe Pivot joint :51 is loca ed mid y between diaphragm follower screws52 and 53 which engage the d p a m 9 h m e 42 a d r specl e y- Lever 48carries a third diaphragm follower screw 54 which engages the diaphragmof pilot chamber 44. An adjusting springfill' engages-the lever 48, .asshown.

Because of the .egualtareas of the diaphragms in chambers 42 and 43 andthe location of pivot 51, the position of lever 48 is indiiierent to thepressure which exists in the outlet connection 39. Thus, it will beapparent that as pressure in ,the pilot chamber 44 increases, thelefthand end of lever .48 will move downward, causing the supply valveto open and admit pressure fluid from the supply connection 38 into thechambers 42 and 43. This pressure fluid, in turn, flows to the outletconnection 39.

As shown in fig. 1, the outlet connection 39 of the piloted relay 19 isconnected to branch line 23 and therebyt e n et of the selecto val e -1cse out et, :i turn. is connected to supply pressure 'fluid to thedamper motor 16. Movement oi the d mper ,rnotpr 16, in response to aation 9? t e Pis n ts p ly o c o l y e t ns an o some 55.- Th s spri 5is ne ween t e movab e element f m o 16 4 e a m 5.6 Rete r ns a ai o i5. it will be seen. th t he ar Se s ri idly connected o the lever .48.and n reasi spr n tensi n sen es he arm 6. to are: i cpp s wi o the r ssin ch r 44, r y causing the lever 48 to return to its balanced positionin h h the Su pl and al alv a e pp d.- A duction of pressure in thechamber 44 will cause the ever 8 t barn t e h ust a e, the e y entin pes-v sure fluid from the outlet connection 39 which will have thefiecrofr u in the tensi n n th pr 5 w er y the lever .48 is resto'red toits balanced position to again lap the supply and exhaust valves. Fromthis, it will be apparent that the pressure present in the outletconnection 39 Will in accordance with variations of the pressure in thechamber .44. The pilot connection 41 s shaw sti ate wi th b anch i 2 fthe thenmostat 21 in Fig. 1 The outlet connection 39 is con: nectedbranch line 23, while the supply connection 38 connected to the airsupply, as shown.

Refer again to Fig. 1. Relay 18 is a pneumatic relay of the type shownon the Otto Patent 1,500,260 assigned to applicantls assignee. The lidwhich controls the bleed port is connected to be shifted progressivelyby a solenoid which is energized by the current flow through the sec.-ondary circuit of a transformer 57 whose primary wind,- ing is connectedin series with the compressor motor Th pr s re in he branc i n 2 of thisre ay remains constant so long as motor current is below a prescribedamount; When this current is exceeded, the relay ii checked-i s. will ineas ts r nc n pressure. it it rcversmacting, as it will he in theillustrated preferred crnbodi ent, the branch line pres ure w ll e cd,....c l-

In a typical installation, the supply pressure would be on the order of20 pounds per square inch. The branch line pressure trout the relay iswould vary between 13 d 8 s.i. The pressure in the branch line 24 15p.s. a a luwer limit of .i p.s.i. The pilot relay 19, under the controlof the pressure in branch line 4, might between .8 and 13 p.s.i. Thefluid pressure actuator 16 would be designed to be moved between itsextreme positions by pressures in the8 to 13 p.s.i. range.- v In thenormal operation of'the system, overload cur- 1' woul ny betw en anupper limit o rents would be encountered only under conditions ofabnormally high cooling loads. When abnormally high cooling loads areencountered, the thermostat 21 will increase its branch line pressure,causing pilot relay 19 to increase its branch line pressure and causethe valve 15 to assume its maximum flow position. If the thermostat 21is direct-acting, the pressure in branch line 23 would be 13 p.s.i. Thispressure, formerly the lower one received by selector valve 17, is stillnot greater than the 13 p.s.i. normally present in branch line 22, andthe selector valve will transmit this pressure. This abnormally highcooling load is likely to cause an excessive current to be drawn by themotor. This excessive current will cause a reduction of pressure inbranch line 22, thus immediately causing the selector valve 17 to shiftover and transmit this pressure to the actuator 16. A reduction ofpressure in actuator 16 will permit valve 15 to move toward closedposition. This will, in turn, reduce the tension in spring 55 wherebythe supply valve of the relay 19 will open because the pressure indiaphragm chamber 44 will not have changed. This will charge the branchline 23 with air at 20 psi. In this way, the selector valve is preventedfrom shifting back until the pressure in the thermostats branch line isreduced, which is an indication that the system has restored a propertemperature at the evaporator and need not continue to operate at fullcapacity.

When the overload relay restores its branch line pressure to full value,the valve 15 will again be in maximum open position, restoring thetension of spring 55 and causing the pilot relay 19 to lap. Anyreduction of the pressure in the thermostats branch line will ventpressure from the branch line of relay 19. When this pressure fallsbelow the pressure in branch line 22, the selector valve 17 will resumenormal position and the relay 19 will again be in control to establishthe proper setting of valve 15.

The advantage of this system is that once the overload relay 18 respondsto an overload current, it remains in command until the refrigerationapparatu can meet the cooling demand without producing an overloadcurrent. Thus the system operates at maximum safe capacity to overcomethe abnormal cooling load.

In some installations the stability, afiorded by locating the pilotedrelay 19 in the position shown in Fig. 1. can be sacrificed in order topermit use of the control system to control the operation of more thanone actuator, such as 16. This alternate form of control system is shownin Fig. 2. The reference numerals applied to the components of thissystem are the same as the reference numerals applied to the samecomponents in the Fig. 1 system, except that they are followed by thedesignation prime.

As shown in Fig. 2, the refrigeration system comprises a compressor 11,a condenser 12', an evaporator 13', a throttling valve 15', and a fluidpressure actuator 16' connected to vary the position of the valve 15'.The compressor is driven by an electric motor 14. The control systemcomprises an air supply (indicated by legend), an overload relay 18', aselector valve 17, a thermostat 21', and a piloted relay 19.

As shown, the air supply is connected to supply air to the thermostaticrelay 21' and the overload relay 18'. The branch lines 24' and 22 areconnected to the inlets of the selector valve 17'. The outlet 58 of theselector valve is connected to supply air to the pilot connection of therelay 19'. The supply connection 38' of the relay 19' receives air fromthe air supply and, in accordance with the variation of pressure in theoutlet 58, pilots the admission of air to the fluid pressure actuator 16through the branch line 23'. The outlet connection 58 has a secondbranch 59, as shown, which may be connected to the piloted relay ofother fluid actuators whose operation are to be controlled. Thisarrangement is resorted to because the flow capacity Q of thethermostats 21 and 21' is small ';compared' to that of the relays 19 and19 and it is ,desirable, in order to assure quick response of thecontrolled actua tor, to provide a piloted relay which is directlyassociated with each fluid pressure actuator.

While the embodiment shown in Fig. 2 is not quite as stable underoverload conditions as is the Fig. l embodiment, its operation issatisfactory. It should be particularly noted that in each embodimentthe actuator 16 or 16' is selectively and independently controlled bythe corresponding thermostat or overload relay, depending on the currentdrawn by the motor.

What is claimed is:

1. In a compressor-condenser-evaporator refrigerative circuit unit ofthe type including an electric motor to drive the compressor andthrottling means adjustable to vary the rate of refrigerant flow throughthe compressor, the combination of control means to adjust thethrottling means comprising in combination a fluid pressure-operatedactuator connected with the throttling means to adjust it; a selectorvalve mechanism having two inlet connections and an outlet connection,said outlet connection connected to the actuator; a first fluidpressureoperated relay responsive to a temperature produced by theevaporator and having its branch line connected to supply fluid to oneof the inlets of the selector valve mechanism; a second fluidpressure-operated relay responsive to the amount by which the currentdrawn by the electric motor exceeds a predetermined value, the secondrelay being of a class different from the class of said first relay andhaving its branch line connected to supply fluid to the other inlet ofthe selector valve mechanism; fluid pressure motor means to shift theselector valve mechanism and having two opposed working spaces, eachspace being in constant free flow communication with a different one ofsaid branch lines, the motor means serving in response to a differencebetween the branch line pressure to interconnect the outlet with thatinlet which will cause the actuator to adjust the throttling means toproduce the lower rate of refrigerant flow.

2. The combination defined in claim 1 in which said first fluidpressure-operated relay is a direct-acting relay.

3. In a compressor-condenser-evaporator refrigerative circuit unit ofthe type including an electric motor connected to drive the compressorand means adjustable to vary the rate of refrigerant flow through thecompressor, the combination of control means to adjust theflow-ratevarying means comprising in combination a fluidpressureoperated actuator connected with the flow-rate-varying means toadjust it; a selector valve mechanism having two inlet connections andan outlet connection, said outlet connection connected in flowcommunication with the actuator; a first direct-acting fluidpressure-operated relay having a supply connection, an exhaustconnection and a branch line and including a supply and exhaust valve, avalve operator, a pressure motor connected to said operator and urgingsaid valve toward supply position, and spring means connected betweenthe movable element of said actuator and the operator and urging saidsupply and exhaust valve toward exhaust position,- said relay having itsbranch line connected to one inlet of said selector valve; adirect-acting fluid pressure-operated thermostatic relay, responsive toevaporator temperature and having a branch line connected to supplyfluid to said pressure motor; a reverse-acting fluid pressure-operatedrelay responsive to the amount by which the current drawn by theelectric motor exceeds a predetermined value and having a branch lineconnected to supply fluid to the other inlet of the selector valvemechanism; fluid pressure motor means to shift said selector valvemechanism and having two opposed working spaces, one space being inconstant free flow communication with the branch line of saidreverse-acting relay, and the other being in constant flow communicationwith the branch 7 fine "of said first rlay whereby the pressurediiferential between branch lines controls, the connection of the branchline's beingso chosen that the slector'v'alve mechanism transmits thelower branch line pressure to its outlet.

References Cited in the file of this patent UNITED STATES PATENTS RossJune 3,1958-

